The pathogenesis of malaria has been studied extensively and is described in many scientific publications and review articles [for recent examples see Miller et al., Nature 415:673-679, (2002)]. The causes of the disease are Plasmodium falciparum and to a lesser extent Plasmodium vivax, Plasmodium malariae and Plasmodium ovale. Death by malaria is almost exclusively caused Plasmodium falciparum. The parasites are transmitted by the vector Anopheles gambiae, which preferentially feeds on humans and is long lived. As the mosquito bites, sporozoites are injected into the skin. They travel to the liver, where they pass through several hepatocytes before they establish an infection and divide. Each sporozoite develops into tens of thousands of merozoites, which are released from the liver and invade erythrocytes. Plasmodium falciparum and P. vivax multiply in an asexual manner within erythrocytes. Over a period of two days each merozoite produces about 20 merozoites. The erythrocytes rupture and release merozoites which again invade erythrocytes. The disease begins with the asexual multiplication of the parasite inside erythrocytes. A few merozoites develop into gametocytes, which do not cause disease but transmit the infection to others through female Anopheles mosquitoes. P. vivax develops into gametocytes soon after the release of merozoites from the liver, while P. falciparum gametocytes develop much later.
Malaria is an important health problem in some parts of Asia and South America, and in particular in Sub-Saharan Africa. In any given year nearly 10% of the global population will suffer from malaria—600 million clinical cases. According to recent estimates at least one million deaths occur from malaria each year—a death from malaria every 30 seconds [Greenwood and Mutabingwa, Nature 415:670-672 (2002)]. In Africa malaria kills one out of twenty children before 5 years of age. Recently the malaria situation has deteriorated as a consequence of, among many other factors contributing to the increasing burden of malaria, the most important are the emergence of P. falciparum and P. vivax variants that are resistant to cheap and effective drugs, and the emergence of insecticide-resistant mosquitoes.